A 152,000 BTU burner requires a minimum combustion air duct area of how many square inches.

• A. 20 sq in
• B. 38 sq in
• C. 48 sq in
• D. 60 sq in

Answer: (B)

When sizing combustion air for a gas burner, you use a rule that links the burner’s heat input to the needed duct area. The minimum cross-sectional area of the combustion air duct (in square inches) is found by dividing the burner’s input in BTU per hour by 4,000. This keeps enough air flowing to support complete combustion and prevents negative pressure in the space.

For a burner rated at 152,000 BTU/h, divide 152,000 by 4,000, which equals 38. So the minimum combustion air duct area should be 38 square inches. This matches the standard sizing approach used in practice and on exams, making it the correct selection.